I'm impressed with how polished it is. Seems even more polished than many other Gameloft titles.
My biggest complaint so far are movement/targeting controls. More than once I feel like I've lost control of my character as he goes off to target something when I want to back-off, or I run into the side of the screen and the window doesn't scroll. I imagine with more practice it'll feel more natural.
Also, currently matchmaking takes a while. Hoping that gets better tomorrow.
In the end though, as someone else mentioned, I wonder if the game will maintain a large enough community to survive. By that I mean, it seems like I need to be on wifi, or at least make sure I have a solid internet connection for 30 minutes or so ... I don't know, sure, I can easily put 30 minutes into an iOS game, but that's usually because I let time get away from me. Few games _require_ a gaming session to last 20+ minutes. One of the reason I like iOS games is that I can often play for 5 minutes or less and then put it aside. If I know I have 30 minutes to play something, I'm likely going to play a game on my PC, particularly when the PC experience is still better for that game style/genre (e.g. FPS).
Again, all that aside, it's an impressive mobile MOBA.
Disclaimer: I work on a PC MOBA.